drm/amd/display: Try to acquire a free OTG master not used in cur ctx first

drm/amd/display: Try to acquire a free OTG master not used in cur ctx first

[WHY & HOW]
The current otg master pipe allocation logic is not optimized based
current resource context. We should try to acquire a free OTG master not
used in cur cts first to avoid unnecessary pipe switch from current
state.

Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>